1. Field of the Invention
The present invention relates to a control system for a direct alcohol fuel cell configured to generate electric power using alcohol as fuel.
2. Discussion of the Related Art
A fuel cell, which generates electric power by oxidizing the fuel using oxidant in the presence of oxidation catalyst is well-known in the art. The fuel cell of this kind is configured to start generating electricity when the fuel and the oxidant are supplied to a fuel cell stack thereof, and the fuel cell stack continues the generation process as long as the fuel and the oxidant are being supplied thereto. Therefore, it is preferable to drain the fuel from the fuel cell stack when the power generation of the fuel cell is stopped. For example, Japanese Patent Laid-Open No. 2005-32601 discloses a direct methanol fuel cell system (abbreviated as DMFC hereinafter) using liquid methanol as the fuel, and in order to purge the fuel cell of the liquid methanol, the DMFC taught by Japanese Patent Laid-Open No. 2005-32601 is configured to inversely rotate a feeding pump of the liquid methanol thereby sucking out the liquid methanol remaining in a fuel electrode side of the fuel cell.
According to the teachings of Japanese Patent Laid-Open No. 2005-32601, unconsumed liquid methanol is thus discharged from the fuel cell by driving the feeding pump inversely. Therefore, an electrolyte membrane of the fuel cell can be prevented from being deteriorated by the remaining methanol. For this purpose, the DMFC taught by Japanese Patent Laid-Open No. 2005-32601 requires the pump capable of rotating inversely, as well as a control circuit for rotating the pump inversely. Thus, the DMFC taught by Japanese Patent Laid-Open No. 2005-32601 is structurally complicated by those devices. In addition to the above-explained disadvantage, according to the teachings of Japanese Patent Laid-Open No. 2005-32601, air containing vaporized methanol is discharged from the DMFC to the atmosphere. Consequently, the fuel is wasted and the discharged methanol vapor is harmful for the user. Therefore, the DMFC taught by Japanese Patent Laid-Open No. 2005-32601 has to be improved to avoid those disadvantages.